Galaxy evolution in group environments: The role of preprocessing Gandhali Joshi PhD Committee Meeting 6 July 2017

Introduction Populations of galaxies in groups and clusters vs. field populations: redder, reduced star formation rates,more elliptical morphologies Trends present in lower mass groups => evidence for pre-processing? Possible evolution mechanisms: Local environment based : Harassment, tidal stripping, mergers Global environment based: Starvation, ram pressure stripping Different time scales involved, dependent on location within host group

Aim Understand what are the various processes of galaxy evolution in groups with a focus on mass loss and star formation quenching Establish the degree and importance of pre- processing

Dark Matter Simulation N-body, dark matter simulation using ChaNGa [Jetley+ 2008,2010; Menon+2015] (100 Mpc)3 comoving volume 10243 particles mparticle = 3.7×107 Mʘ 200 snapshots, 68.9 Myr apart. Halo finding using ROCKSTAR [Behroozi+ 2013a] and Consistent Trees [Behroozi+ 2013b]

Project 1: Selecting galaxy analogues Mass      

Project 1: Mass segregation Much noisier trend when considering only massive analogues Significant trend in average mass within 0.5rvir Nearly no trend outside 0.5rvir

Project 2: Mass Loss and Pre-processing Mpeak ~ Mstellar Strong radial trend of mass loss since peak within rvir

Project 2 : Total mass loss Single galaxies retain more mass than grouped galaxies Break separates backsplash galaxies

Project 2: Before & after accretion Before crossing, grouped galaxies lose significantly more mass After crossing, single galaxies lose more mass within rvir, “catch up” to the grouped galaxies

Project 2: Mass loss with time Amount of mass lost is determined by time spent in dense environment Before crossing After crossing

Hydrodynamical Simulation SPH hydrodynamical zoom-in simulation of a galaxy group using Gasoline [Wadsley+ 2004] Group properties: Mvir = 2.7×107 Mʘ Rvir = 788.6 kpc High-res region: mDM = 3.9×106 Mʘ mbaryon = 7.2×105 Mʘ 87 snapshots, 107.64 Myr apart. Halo finding using ROCKSTAR [Behroozi+ 2013a] and Consistent Trees [Behroozi+ 2013b]

Project 3: Mass loss over time Dark matter Gas Significant mass loss in dark matter and gas, but not stars Mass Stars Time

Project 3: Gas mass loss and sSFR Cold gas sSFR Time Similar trends in cold and hot gas Gradual decline in sSFR – faster for grouped galaxies Hot gas Mass Time

Project 3: Radial trajectories Dark matter Single Grouped Distance from group Mass (Time)

Project 3: Radial trajectories Stars Single Grouped Distance from group Mass (Time)

Project 3: Dark matter vs. gas and the role of ram pressure Single Grouped Mgas/MDM Ram pressure Distance from group

Project 3: Implications for galaxy properties Similar gas fractions for all three categories But higher stellar fractions for single galaxies, even higher for grouped galaxies – scatter in SMHM relation? Mstar/Mtot Mgas/Mtot Mtot

Timeline Currently: Completing final science chapter By July 14: Complete thesis draft By July 21: Initiate defense process By Aug 4: Submit thesis Sep 15: Defense

Extra slides

Project 1: Mass segregation Small Groups Large Groups Clusters Segregation trends dominated by small and large groups Nearly no trend seen in clusters

Single Grouped Distance from group Mass